A gas turbine aircraft engine comprises of a compressor compressing ambient air, a combustor burning fuel together with the compressed air and a turbine for powering the compressor. The expanding combustion gases drive the turbine and also result in thrust for propelling the aircraft.
A gas turbine aircraft engine is equipped with various sensors for measuring the performance of the engine. One of many parameters measured is the engine pressure ratio (EPR). The EPR is a widely used parameter used for engine thrust settling. EPR is derived from gas pressure sensors installed in the engines gas path. One typical installation of EPR sensors is immediately downstream of the last stage of the turbine. In this position, the sensors are exposed to the exhaust gases of the engine. Exhaust gases comprises air and combustion products. Specifically, the exhaust gases contain particles in form of un-combusted fuel and combustion products such as coke and ash. Further the exhaust gases contain air foreign particles. Small particles have the ability to find their way into cavities of objects in the gas path such as the air passage of the probe for pressure measurement used in EPR estimates. Particles entering the probe may partially block the air passage and thereby restrict the air flow. Particles entering the probe may totally block the passage to the sensors. A partially blocked or totally blocked passage results in a false pressure indication or no pressure indication at all. To restore the probe to prime working condition, the aircraft maintenance procedure calls for dismantling the probe from the engine and have it cleaned or replaced with a replacement probe. This is a time consuming and costly operation due to the fact that there are multiple of these probes on each engine and in case of improper instrument reading all probes will have to be removed and cleaned.
In actual aircraft installations there are multiple probes. Each one is connected via a conduit to a manifold which in turn is connected to a pressure sensing device. The pressure sensing device generates a signal to a pressure ratio transmitter which in turn delivers a signal to the EPR instrument. The use of multiple probes allows for one or a portion of the probes being blocked without giving a false EPR reading. However, when instable EPR instrument readings are observed it is often an indication that probes are blocked.
According to aircraft maintenance routines a blocked probe is put into service again by a replacement probe or by cleaning the blocked probe. Cleaning may be the preferred action for reason of saving costs as the same probe is used again. Cleaning is conducted by dismantling the probe from the engine and cleaning according to a cleaning procedure.
Consequently, there is a great need of a method and an apparatus that provides for an efficient, both in terms of cleaning efficiency and time consumption, and cost-saving cleaning of a set of measuring probes of a gas turbine engine of an aircraft.